This application is based on patent application No. 30132/1997 filed Feb. 14, 1997 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to an ink jet print apparatus and method for ejecting inks to form ink liquid droplets and depositing them on a printing medium such as paper for printing, and in particular, to a configuration for preventing an ink jet head from inappropriately ejecting inks due to the splashing of ejected liquid droplets occurring on the printing medium.
2. Description of the Related Art
Due to the use of non-impact printing method, ink jet print apparatuses have various advantages such as low noise during printing and fast printing, and are gathering attention due to their ability to provide significantly saturated color images. In such ink jet print apparatuses which use thermal energy to eject inks, since the ink jet head can be manufactured using processes similar to those for semiconductor devices, the size of the apparatus can be easily reduced, while the number and density of orifices used can be easily increased.
Printing color images using such ink jet print apparatuses has many advantages. A plurality of types of inks, for example, yellow, magenta, cyan, and black corresponding to colors to be printed are generally ejected from heads for the respective inks in such a way that these inks are deposited on one another substantially at the same position on the printing medium in order to form desired color dots.
In addition, to improve the water-proofness of printed images and print grade, the present applicant has proposed a print apparatus that ejects a processing liquid (also referred to as a printing quality improvement liquid) that makes the color material in an ink insoluble or aggregation in such a way that the liquid is deposited on the ink. This configuration can mix the ink with the processing liquid on the printing medium to make the color material such as a dye in the ink insoluble in order to improve water-proofness. It can also prevent the ink from bleeding and increase the concentration to improve the print grade.
If, however, color printing is performed as described above or the processing liquid is used, a subsequent ink or the processing liquid deposits in a overlay manner on a liquid droplet of an ink or the processing liquid that is precedently deposited on the printing medium and that is permeating therein, so splashing is more likely to occur and a larger amount of liquid droplets splashes than in the case where an ink droplet is deposited on the printing medium without depositing a precedent or leading ink. Such splashing droplets or processing liquid droplets, or splashing liquid droplets into which an ink and the processing liquid are mixed together, deposit on the face (in which ejection ports are disposed) of the ink jet head like mists, thereby deflecting the ejection direction or preventing ejection which affects the grade of the images.
In particular, if splashing liquid droplets in which an ink and the processing liquid are mixed together deposit on the face, they become insoluble on the face and cannot be easily removed by recovery processing, such as wiping or preliminary ejection, resulting in a critical ejection error.
It is a first object of this invention to provide an ink jet print apparatus that can prevent ejection errors by reducing the amount of splashing liquid droplets of an ink or the processing liquid that are deposited on a face of the ink jet head, including an ink or processing liquid ejection port.
In addition, it is a second object of this invention to provide an ink jet print apparatus that can prevent ejection errors by reducing the amount of splashing liquid droplets of an ink or the processing liquid that are deposited on the face of the ink jet head.
The first object is to provide an ink jet print apparatus for printing and can be achieved by one aspect of this invention using an ink jet head that ejects a liquid from at least two ejection ports to allow liquids sequentially ejected from the at least two ejection ports, as the ink jet head and a printing medium are relatively moved to deposit on the printing medium in such a way that the liquids are deposited on one another on the printing medium, wherein a velocity vector of the liquid ejected from at least one of the at least two ejection ports has a component of the velocity vector in the direction opposite to the relative moving direction of the ink jet head and the printing medium.
Here, the velocity vector of a subsequent one of the liquids sequentially ejected from the at least two ejection ports may have a larger component of the velocity vector in the direction opposite to the relative moving direction than a velocity vector component of a leading liquid.
The second object is to provide an ink jet print apparatus for printing and can be achieved by a second aspect of this invention using an ink jet head that ejects a liquid from at least two ejection ports in order to allow liquids sequentially ejected from the at least two ejection ports as the ink jet head and a printing medium are relatively moved to deposit on the printing medium in such a way that the liquids are deposited on one another on the printing medium, wherein a velocity vector of the liquid ejected from at least one of the at least two ejection ports has a component of the velocity vector in the direction opposite to the relative moving direction of the ink jet head and the printing medium.
Here, the velocity vector of a subsequent one of the liquids sequentially ejected from the at least two ejection ports may have a larger component of the velocity vector in the direction opposite to the relative moving direction than a velocity vector of a leading liquid.
According to this invention, at least one of the velocity vectors of the liquids sequentially ejected from the at least two ejection ports in the ink jet head as the ink jet head is scanned has a component of the velocity vector in the direction opposite to the relative moving direction. Thus, the direction in which the subsequently ejected liquid is ejected can be tilted toward the direction opposite to the relative moving direction relative to the printing medium, thereby enabling a splashing liquid droplet caused by the depositing on an already deposited liquid droplet of the subsequent liquid droplet, to be directed away from the ink jet head.
The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.